Bleomycin is an antitumor antibiotic used clinically for the treatment of squamous cell carcinomas and malignant lymphomas. The mechanism by which bleomycin acts as an anticancer agent is believed to involve scission of single- and (especially) double-stranded DNA, the latter of which can be cleaved through both strands by the antibiotic. We propose a biochemical study to identify the molecular mechanism of DNA cleavage by bleomycins. Specifically, we will synthesize chemically oligonucleotides of varying length having a single preferred bleomycin recognition site. We will use the oligonucleotides in NMR studies to identify (1) the structural features in DNA that facilitate bleomycin binding and cleavage, (2) the possible participation of both "structural domains" of bleomycin in DNA binding and (3) the possibility that the "active" bleomycin-metal complex undergoes ligand exchange with DNA upon binding to the oligomer. Additionally we will attempt to elucidate the molecular mechanism of DNA cleavage by (1) enzymatic degradation of the chemically synthesized oligomer after bleomycin treatment and comparison of fragments with chemically synthesized species and (2) the use of deoxy-oligonucleotides radiolabeled at key sites. Finally, we will investigate the nature of cleavage of DNA by Cu(II)-bleomycin (a species reported erroneously to be dysfunctional), which may actually represent the "physiologically relevant" form of the antibiotic.